| Phosphorus chemical industry is one of the indispensable industries in national economy.The main product of thermal process phosphoric acid is the basic raw material for the production of organic phosphorus chemicals.At present,the production of yellow phosphorus is mainly made by electric furnace,with the Waste energy consumption.Because of the corrosion of the material,the yellow phosphorus exhaust,which accounts for 32%of the total energy consumption of yellow phosphorus production,has not been effectively utilized,which restricts the development of the chemical industry.In this paper,as the main object of study,according to the utilization of low temperature heat of tail gas of yellow phosphorus(?300 ?)period of phosphate corrosion of boiler,the P2O5-H2O system gas liquid equilibrium research was carried out to reap the composition of phosphoric acid in the system P2O5-H2O at low temperature.And several typical equilibrium temperatures and the corresponding concentration of phosphoric acid products were determined,and then seven kinds of materials were chosen to study the corrosion.Based on the study,the conclusions could be obtained as following.The device for determining the gas liquid balance of P2O5-H2O system was designed to reap the composition of phosphoric acid in the system P2O5-H2O under atmospheric pressure.Then,the equilibrium temperature and vapor phase composition of different liquid concentrations at atmospheric pressure were obtained by the P2O5-H2O system of vapor-liquid equilibrium apparatus,a gravimetric method was used by molybdenum phosphate precipitation agent for determining the concentration at 100 ??150??200? and 300 ? of acids that contained 17.66%?61.66%?69.60%?75.37%P2O5.The influences of heating rate and gas flow rate on the thermal decomposition kinetics of phosphoric acid had been studied.Kinetics of phosphoric acid is classified into two types by the concentration of phosphoric acid 100%H3PO4 as the boundary.The first type was lower than the concentration of 100%H3PO4,with four kinetics temperature zone.The first stage was the corresponding of poly phosphoric acid dehydration;the second stage was the corresponding polymerization and dehydration,with a small amount of phosphorus compounds from orthophosphoric acid;The third stage was the corresponding phosphate prolapsed large molecular rapid evaporation;the fourth stage residue volatilization.The second type was higher than 100%H3PO4 concentration.Because the polyphosphate containing less free water,olio phosphate mass loss was not obvious,as the increase of the concentration of polyphosphate mass loss disappeared,so polyphosphate in the first stage of the main kinetics,DTG peak was not obvious or not.The second main stages of kinetics as same as orthophosphoric acid which was lower than 100%H3PO4.Ultimately,the uniform corrosion behavior and characteristics of carbon steel,09CrCuSb,Ti,304,310S,316L and 904L at different equilibrium temperatures was researched.the corrosion tests show that the uniform corrosion resistance of 316L and 904L is significantly better than carbon steel?09CrCuSb?Ti?304 and 310S at 100??150??200? and 300?,and because of 904L with high Ni content,it had even better corrosion resistance than 316L.But 904L was expected to be used to harsh environment,such as heat recovery of yellow phosphorus exhaust and enrichment process of in furnace process phosphoric acid.The EDS analysis of passive film formed on 904L show that the formation of corrosion resistance element Ni could restrain corrosion occurs.By forming passive film,Ni prevented corrosive substance through the passive film,and improved local corrosive environment. |
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